/Engine/Source/Editor/UnrealEd/Public/Kismet2/KismetEditorUtilities.h
Take a list of Actors and update an existing Blueprint by harvesting the components they have. Essentially HarvestBlueprintFromActors, but updates an existing Blueprint rather than creating a new one.
The updated blueprint, or null if it failed somehow
static [UBlueprint](API\Runtime\Engine\Engine\UBlueprint) * UpdateExistingBlueprintFromActors ( const [FString](API\Runtime\Core\Containers\FString) & Path, const [TArray](API\Runtime\Core\Containers\TArray)< [AActor](API\Runtime\Engine\GameFramework\AActor) * > & Actors )